Attachment for sewing machine



0a. 14, 1969 c. WHITE 3,472,189

ATTACHMENT FOR SEWING MACHINE Filed June 20, 1967 United) States Patent Us. Cl. 112-452 Claims ABSTRACT OF THE DISCLOSURE An attachment for a sewing machine, which includes a cutter blade and a holding pad arranged to be raised and lowered at a position situated on the output side of th stitching mechanism of the sewing machine with the said pad nearer the mechanism, and two detector devices arranged one between the stitching mechanism and the pad and the other on the other side of the blade, the detector devices being adapted so that only in the absence of material at both detector devices is the blade lowered to cut any threads located beneath it and the pad lowered to trap and hold the ends of such threads.

This invention relates to an attachment which may be fitted to a sewing machine, particularly an industrial sewing machine, for the purpose of cutting the threads at the end of a sewing operation to permit the removal of completed work and also holding the ends of threads still passing through the needle of the machine so that the needle cannot become inadvertently unthreaded due to continued operation of the thread take-up mechanism of the sewing machine.

The present invention consists in an attachment for a sewing machine of the type having a threaded needle movable towards and away from a base plate, comprising a cutter blade mounted for movement between cutting and non-cutting positions, a holding pad means connected to the cutter blade, for therewith movement and adapted to trap the thread when the cutter blade is in cutting position, and control means for moving the cutter blade between cutting and non-cutting positions so that the blade is maintained in cutting position and thereby the thread is held to prevent unthreading of the needle.

In carrying the invention into elfect according to one convenient mode by way of example, the accompanying drawing shows diagrammatically the operation of an attachment used in association with a sewing machine.

The attachment includes a combined thread cutting blade 1 and thread holding a resiliently flexible rubber pad 2 suitably mounted along the lateral face of the cutting blade by means (not shown) for movement in unison in a vertical direction between a raised position in which the blade 1 and pad 2 are clear of a base plate 3 and a lowered position, as shown in the drawing, in which the blade 1 and pad 2 engage the plate 3, the blade 1 cutting any threads which pass under it and the pad 2 trapping the ends of the threads cut in this way.

In front of the pad 2 there is provided a conventional stitching mechanism including a foot 4 and a needle 5, and the drawing shows material 6 in the process of being stitched as at 7.

Also in front of the pad 2, there is provided a nozzle 8 directing a jet of air into an aperture 9 connected to a diaphragm valve 10 and similarly on the side of the blade 1 there is provided a further nozzle 11 directing a jet of air into a further aperture 12 connected to a further diaphragm valve 13.

The two diaphragm valves 10 and 13 are etiectively connected in series to a source 14 of compressed air and lice arranged so that only if jets of air enter both apertures 9 and 12 will compressed air be supplied to the output line 15 which is connected to a piston arrangement which causes lowering of the blade 1 and pad 2. Thus when both apertures 9 and 12 are uncovered, the blade 1 and pad 2 will be lowered (as shown in the drawing), but should either or both apertures be covered, then the blade 1 and pad 2 will be raised.

The accompanying drawing shows the initial starting position in which the two apertures 9 and 12 are uncovered and consequently the blade 1 and pad 2 are lowered, with the pad 2 trapping the ends of threads 16 after cutting them at the end of a previous sewing operation. Material 6 is being stitched as it is fed underfoot 7.

When the leading edge of the material covers the first aperture 9, the blade 1 and pad 2 will be raised to permit the material to pass underneath them. Subsequently, the material will cover aperture 12 but as previously explained this will not alfect the raised position of the blade 1 and pad 2.

After the stitching operation has been completed the piece of material 6 will be drawn forward by hand or other means together with threads attached to it, first uncovering aperture 9 and then aperture 12.

At this moment, the blade 1 and pad 2 are lowered to cut the threads and trap their free ends in the initial position shown in the drawing.

Any backward pull on the threads due to continued operation of the thread take-up mechanism, which could cause unthreading of the needle 5, is resisted by the clamping of the thread ends between pad 2 and base plate 3. The sewing machine is thus maintained in a condition in readiness to perform a further sewing operation.

It will be appreciated that the attachment described above also has the advantage that the finger of an operator cannot be caught accidentally beneath the blade 1 since any interruption of the jet from either nozzle caused by the presence of a finger will immediately cause the blade 1 to be raised.

Various modifications may be made within the scope of the present invention. Thus, for example, the blade 1 and pad 2 may be raised and lowered electromagnetically, and the detection system consisting of nozzles 8 and 11 and apertures 9 and 12 may be replaced by other mechanical or electrical or electronic systems.

I claim:

1. An attachment for a sewing machine of the type having a threaded needle movable towards and away from a base plate, comprising a cutter blade mounted for vertical movement towards and away from the base plate corresponding to cutting and non-cutting positions, a holding pad means rigidly connected to the cutter blade for movement therewith and adapted to trap the thread against the base plate when the cutting blade is in cutting position, and control means for maintaining the cutting blade in non-cutting position until a workpiece is moved past the cutter blade, whereupon the cutter moves into cutting position and thereby the thread is held to prevent unthreading of the needle.

2. An attachment according to claim 1, wherein the holding pad means is formed of a resiliently flexible rubber material and is mounted along the lateral face of the cutting blade adjacent the threaded needle and the lower edge of the holding pad means being aligned with the cutting edge of the blade for trapping the thread against the base plate.

3. An attachment for a sewing machine of the type having a threaded needle movable towards and away from a base plate, comprising a cutter blade spaced from the threaded needle and mounted for vertical movement towards and away from the base plate corresponding to cutting and non-cutting positions, a holding pad means rigidly connected to the cutter blade between the blade and the needle for movement therewith and adapted to trap the thread against the base plate when the cutting blade is in cutting position, a first detector device arranged between the threaded needle and the holding pad means and a second detector arranged on the side of th cutting blade remote from the threaded needle and control means actuated by said first and second detectors moving the cutting blade into cutting position only when both said first and second detector devices are operative, said cutting blade maintained in non-cutting position when at least one of said detectors is inoperative.

4. An attachment according to claim 3, wherein each of the detectors includes a nozzle directing a jet of air 15 aperture is connected to a diaphragm valve,-the two valves being efiectively connected in series.

References Cited UNITED STATES PATENTS 1,592,115 7/1926 Lindgren 112-252 1,846,628 2/1932 Castagna 112--252 2,229,991 1/1941 Sauer 112252 2,418,356 4/ 1947 Kleber.

2,423,080 7/ 1947 Belcher.

3,359,931 12/ 1967 Miller 112-252 X 2,376,417 5/ 1945 Chudner 112253 X 2,707,927 5/ 1955- Artzt 112-253 X 2,997,009 8/ 1961 Ballard 112-253 X HERBERT F. ROSS, Primary Examiner 

